SALT LAKE CITY (AP) — Utah doctors are calling for a boycott of a medical-waste incinerator in an effort to shut it down as the company fights emissions violations and faces a special investigation ordered by the governor.

The Utah Physicians for a Healthy Environment stepped up its campaign against Stericycle Inc. by asking customers to stop doing business with the company’s burn plant in North Salt Lake. The investigation by state health authorities is doing little but delaying action against the company, the group added.

Local residents and clean-air advocates say clinics and hospitals have cleaner and cheaper ways to get rid of infectious material, pharmaceuticals and syringes through chemical or ozone disinfectant. Doctors say the waste doesn’t have to be burned and can be shredded for regular landfill disposal instead.

“The medical research confirms our fears that our children are being harmed by this incinerator,” Alicia Connell of Communities For Clean Air told reporters at a news conference Thursday. “There is no reason to continue incinerating medical waste when there are cleaner and safer alternatives.”

Gov. Gary Herbert told reporters Thursday that he was “very concerned” about the incinerator and has ordered a three-part investigation of Stericycle’s operation. In a citation filed in May, state regulators said Stericycle released cancer-causing dioxins and other pollutants at times going back years and rigged smokestack tests to cover it up.

The case gained national attention with a YouTube video showing a billowing black cloud over the incinerator on Sept. 6.

Herbert said he didn’t know anything about company plans to possibly move out of North Salt Lake, as reported weeks ago by the city’s mayor.

“We go out there each and every day to make sure they’re in compliance with their permit,” Herbert said Thursday.

For months, Lake Forest, Ill.-based Stericycle has consistently avoided making any public comment about its Utah operation. The company’s corporate communications office didn’t return messages left Friday by The Associated Press.

Herbert’s health department released the first part of its investigation earlier this week. Officials said 10-year-old soil samples kept in storage showed scant traces of dioxins, the chemicals that doctors say raise the biggest health concern. State officials now plan to take fresh soil samples from housing subdivisions around the incinerator.

Doctors say soil samples are beside the point. Dioxins don’t persist in soil because they eventually vaporize or are taken up by plants, and the incinerator emits plenty of other toxins, they say.

Stericycle’s permit allows the Utah incinerator to release up to 9.5 tons of hazardous pollutants, including mercury and lead, every year.

“Living near an incinerator, or having your body contaminated with incinerator toxins originating miles away, statistically increases your chance of many types of serious diseases,” said Brian Moench, president of Utah Physicians for a Healthy Environment. “We don’t need to wait for a study specific to confirm that.”

The physicians’ group is asking customers of Stericycle to switch disposal services by Jan. 1.

“It is long overdue that medical facilities discontinue the practice of having their waste incinerated,” the group’s letter reads. “The residents nearby are determined to protect their children, families and neighborhood, and will do whatever it takes to close the incinerator.”

The Stericycle plant burns about 7,000 tons of waste annually, including human tissue, from Utah and other states, according to the Utah Department of Environmental Quality.